diff --git a/core/modules/locale/locale.test b/core/modules/locale/locale.test
index 42a0fbd..465d741 100644
--- a/core/modules/locale/locale.test
+++ b/core/modules/locale/locale.test
@@ -617,6 +617,15 @@ class LocalePluralFormatTest extends DrupalWebTestCase {
       'langcode' => 'hr',
     ));
 
+    // Attempt to import some broken .po files as well to prove that these
+    // will not overwrite the proper plural formula imported above.
+    $this->importPoFile($this->getPoFileWithMissingPlural(), array(
+      'langcode' => 'fr',
+    ));
+    $this->importPoFile($this->getPoFileWithBrokenPlural(), array(
+      'langcode' => 'hr',
+    ));
+
     // Reset static caches from locale_get_plural() to ensure we get fresh data.
     drupal_static_reset('locale_get_plural');
     drupal_static_reset('locale_get_plural:plurals');
@@ -656,6 +665,7 @@ class LocalePluralFormatTest extends DrupalWebTestCase {
     $name = tempnam('temporary://', "po_") . '.po';
     file_put_contents($name, $contents);
     $options['files[file]'] = $name;
+    $options['mode'] = LOCALE_IMPORT_OVERWRITE;
     $this->drupalPost('admin/config/regional/translate/import', $options, t('Import'));
     drupal_unlink($name);
   }
@@ -706,6 +716,41 @@ msgid "Monday"
 msgstr "Ponedjeljak"
 EOF;
   }
+
+  /**
+   * Returns a .po file with a missing plural formula.
+   */
+  function getPoFileWithMissingPlural() {
+    return <<< EOF
+msgid ""
+msgstr ""
+"Project-Id-Version: Drupal 7\\n"
+"MIME-Version: 1.0\\n"
+"Content-Type: text/plain; charset=UTF-8\\n"
+"Content-Transfer-Encoding: 8bit\\n"
+
+msgid "Monday"
+msgstr "lundi"
+EOF;
+  }
+
+  /**
+   * Returns a .po file with a broken plural formula.
+   */
+  function getPoFileWithBrokenPlural() {
+    return <<< EOF
+msgid ""
+msgstr ""
+"Project-Id-Version: Drupal 7\\n"
+"MIME-Version: 1.0\\n"
+"Content-Type: text/plain; charset=UTF-8\\n"
+"Content-Transfer-Encoding: 8bit\\n"
+"Plural-Forms: broken, will not parse\\n"
+
+msgid "Monday"
+msgstr "Ponedjeljak"
+EOF;
+  }
 }
 
 /**